The National Archives informed Congress that its staff had obtained nine boxes of materials from the Boston office of President Joe Biden’s personal attorney.

A letter sent this week to a pair of Republican senators reportedly reveals new information about the investigation into Biden’s handling of government documents, specifically about Patrick Moore, the attorney identified as the one who discovered classified materials while packing up the president’s former think tank office in early November.

“When NARA [National Archives and Records Administration] contacted President Biden’s personal counsel on November 3, 2022, to arrange to pick up boxes from the Penn Biden Center in Washington, D.C., they informed NARA that Mr. Moore had moved other boxes from the Penn Biden Center to Mr. Moore’s law firm in Boston,” Acting Archivist of the United States Debra Steidel Wall wrote in the letter dated Tuesday.

Wall revealed that the National Archives was informed by Biden’s counsel that their review of the materials in the Penn Biden Center began in October 2022 — earlier than previously known — and that some boxes were moved to Boston at some point afterward.

“NARA staff retrieved nine boxes from Mr. Moore’s Boston office” at the request of the Justice Department on November 9 and these boxes were secured in the John F. Kennedy Presidential Library in Boston, Wall wrote. It is not clear whether there is any classified materials in these boxes, as Wall noted that her agency “has not reviewed the contents of the boxes found at Mr. Moore’s Boston office.”

The letter is addressed to Senators Chuck Grassley (R-IA) and Ron Johnson (R-WI), both of whom have written to Wall seeking more information about the discovery of classified documents dating back to Biden’s time as vice president and U.S. senator in multiple locations.

The documents controversy began in early November, when Biden’s attorneys discovered approximately ten classified records while clearing out Biden’s office at the Penn Biden Center, according to his legal team. The discovery, however, was not made public until CBS News broke the story of an investigation by US Attorney John Lausch. Following the revelation, Biden stated that his team immediately contacted the National Archives to request the materials.

Following the initial review by Lausch, Attorney General Merrick Garland appointed former U.S. Attorney Robert Hur as special counsel to examine whether “any person or entity violated the law in connection with this matter.”

According to CNN, Moore met with a team led by Lausch during the initial review of the president’s handling of documents. A Freedom of Information Act request revealed emails indicating Moore was in contact with the National Archives about picking up boxes of materials from his office on November 9, though the number of boxes was not specified at the time the Washington Examiner reported on it last month.

The FBI has conducted document searches at Biden’s home in Wilmington, Delaware, his beach house in Rehoboth, Delaware, and the Penn Biden Center, a think tank in Washington, D.C., which have yielded additional materials of interest to investigators. Throughout the process, Biden’s personal attorneys and the White House have insisted on cooperating with the National Archives and the Justice Department.

Classified documents have also been discovered in the homes of former President Donald Trump, who is being investigated by a separate special counsel, and former Vice President Mike Pence, prompting the National Archives to urge other former presidents and vice presidents to conduct similar searches.

Senator Mark Warner, chairman of the Senate Intelligence Committee, warned leaders of the United States intelligence community on Wednesday that a lack of transparency to Congress about the documents could jeopardize the Biden administration’s efforts to renew a surveillance law this year. “This trust relationship has to be reciprocal,” he said.